extension StringPhone on String {
  String get phone {
    var _mobile = this;
    if (_mobile.length > 4) {
      var sufixLength = (_mobile.length - 4) ~/ 2;
      var prefixLength = _mobile.length - 4 - sufixLength;
      return _mobile.substring(0, prefixLength) +
          '****' +
          _mobile.substring(_mobile.length - sufixLength, _mobile.length);
    } else {
      return _mobile;
    }
  }
}
